gun*_*har 3 software-center update-manager
我从 Ubuntu 12.04 升级到 Ubuntu 12.10。在此之后，它不再更新。软件更新程序出现此错误：
W:Failed to fetch http://archive.canonical.com/ubuntu/dists/precise/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/quantal/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal-updates/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal-backports/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal-security/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal-proposed/Release.gpg Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal/restricted/source/Sources Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal/main/source/Sources Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal/multiverse/source/Sources Unable to connect to 10.4.42.15:8080:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal/universe/source/Sources Unable to connect to 10.4.42.15:8080:
:
W:Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/quantal-proposed/universe/i18n/Translation-en Unable to connect to 10.4.42.15:8080:
E:Some index files failed to download. They have been ignored, or old ones used instead.
我无法从软件中心安装任何东西；它只是要求使用这个源，然后它只是继续查询软件源，什么也没有发生。
内容为/etc/apt/sources.list：
#deb cdrom:[Ubuntu 12.04 LTS _Precise Pangolin_ - Release i386 (20120423)]/ precise main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://us.archive.ubuntu.com/ubuntu/ quantal main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ quantal restricted main multiverse universe #Added by software-properties
## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ quantal-updates main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ quantal-updates restricted main multiverse universe #Added by software-properties
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ quantal universe
deb http://us.archive.ubuntu.com/ubuntu/ quantal-updates universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://us.archive.ubuntu.com/ubuntu/ quantal multiverse
deb http://us.archive.ubuntu.com/ubuntu/ quantal-updates multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ quantal-backports main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ quantal-backports main restricted universe multiverse #Added by software-properties
deb http://us.archive.ubuntu.com/ubuntu/ quantal-security main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ quantal-security restricted main multiverse universe #Added by software-properties
deb http://us.archive.ubuntu.com/ubuntu/ quantal-security universe
deb http://us.archive.ubuntu.com/ubuntu/ quantal-security multiverse
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu precise partner
deb-src http://archive.canonical.com/ubuntu precise partner
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu quantal main
deb-src http://extras.ubuntu.com/ubuntu quantal main
# deb http://download.learnfree.eu/repository/skss / #SKSS
# deb-src http://download.learnfree.eu/repository/skss / #SKSS
deb http://us.archive.ubuntu.com/ubuntu/ quantal-proposed restricted main multiverse universe
deb-src http://us.archive.ubuntu.com/ubuntu/ quantal-proposed restricted main multiverse universe #Added by software-properties
终于找到了ubuntu 12.10没有更新问题的解决方法。代理实际上存在一些问题，所以我所做的如下：
我跑去gksudo gedit /etc/apt/apt.conf 编辑apt.conf文件，然后
在apt.conf文件中添加以下行：
Acquire::http::Proxy "false";
现在一切都像以前一样顺利。